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Discussion Starter #1
Ok today I have installed a new abs accumulator and now my pump only runs after every third brake application - previously it was running after every pump.
Now I have found two other things that may or may not be related.
Firstly: I have found that, if I turn off and then immediately turn on again, my pump runs for about two seconds. This is happening with a fully pressurised system.
Secondly: If I leave my beast switched off for about an hour and a half it then takes another 25 seconds to repressurise the system. Again this is on a fully pressurized system.

I do realise that there is a very slow bleed back into the master cylinder but the 2nd item seems just a bit fast. Maybe my pump is becoming worn and so the increased internal tolerances are allowing this to happen.

As for the 1st item I have no idea why it is apparently dropping below minimum pressure (from fully charged) in less than one second. As I understand it there is a pressure range and the pump only kicks in when the lower value is reached.

Any thoughts or ideas are welcome - or are these occurances normal.

Rowan
Thanks to Sam at Island 4x4 for wonderful service - even allowing for some stupid Icelandic volcano.
 

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Mine does this. Has always seemed normal to me. Mine pressurizes in about 20 seconds though... As long as the pump isn't making any ticking noises and you have power brakes when you need them, and there are not lights, you are probably fine.
 

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Discussion Starter #5
Thanks all.
Shupack I didn´t bleed it down - I just let it build up to maximum pressure and left it to make sure that everything was ok. I went back out 1 1/2 hours later and it had naturally bled down that much pressure. From totally bled down (30 pumps, wait, then 30 again) to total pressure takes 32 seconds (timed).

I am just being cautious about what it should really do - that is why I thought that my pump is just becoming worn - although it doesn´t make any funny noises and just humms away to itself. I don´t know how long my old, knackered accumulator was on it but I reckon some time (going by what else has needed work) and so the extra work time might have shoutened it´s life and I don´t really want it to pack-a-sad at the wrong time.

As for the bleed-down time I think that it should be a whole lot slower ie overnight instead of over lunchtime. By the look of their construction the fluid can only back-bleed back past the pistons thingeys so maybe they are worn and allowing this to happen.

Davey this is my only pump so I can´t swap parts around and, from what I gather, the electric motor is fixable but the pump is not (no parts available).
 

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Take my word for it, LEAVE IT ALONE! lol. The system is very complex and is a PIA. I've rebuilt mine. As long as it runs smooth and it pumps, leave it alone. If you want more info, I did a little write up on it: http://yourwebdesigns.com/abpmp/ . Your relief valve (which means time for a new pump) or the pressure switch could potentially be going out. If I leave mine for a couple hours, it too bleeds down. However, mine doesn't come back on after I turn the car off and turn it back on :think: . How often does the pump come on when the vehicle is sitting there running at idle and for how long did you drive the RR with the faulty accumulator, causing it to come on at every application?
 

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Discussion Starter #7
OK - if it works then I won´t @$*& with it. I have good brakes and everything else works so I am happy.

I have had my P38 for about 6 months (114700K) but only realised/suspected that my accumulator was worn out a couple of months ago. It had now done 117600K. Then it was a case of obtaining a new one - I made a shopping list of other things that had been neglected by previous owners and put in one order for the lot. Island 4x4 were by far the cheapest - even including air postage from England to New Zealand.

I will check tomorrow regarding what happens when it is left idling - maybe it will come again like has happened to others. Then it might just be new pump time but we will see.

Cheers
 

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Discussion Starter #8
This afternoon I checked to see if my abs pump was allowing bleed-back without touching the brakes. I was working under the bonnet around the fan belt and water pump and couldn´t run the engine so I just turned the ignition on, let it build up pressure (28 secs this time) and left the key on. Sure enough it came on again after about 20 minutes and ran for a period of, maybe 10-15 seconds (no watch handy). At this point I switched off and then turned it back on immediately and, lo and behold, it ran again for a couple of seconds - this was straight after it had reached full pressure and cut out.

Very strange but unfortunately I have no idea how long it had been used with the worn out accumulator - I only discovered it when I changed the brake fluid a couple of months ago.
I will keep using this pump as it still has some life left in it but will keep my eyes open for a deal on another one. At least it is only running every third brake press with the new accumulator but still not enough.
 

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Discussion Starter #9
A thought just occured to me - is it possible that the bleed-down problem I am having is caused by the master cylinder/modulator somehow leaking inside? I am not familiar with their internals so maybe this is not possible.

Is it a possibility?
 

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lrscott said:
Take my word for it, LEAVE IT ALONE! lol.
Take the Man's advice and leave it alone, mine takes around 30-35 secconds to build up pressure and three good applications of the brake's and it cut's in again been like that for the 8 year's i have owned the truck, changed the accumulator once in that time and have never had any problems with the brake's.

Cheers
 

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Rowant said:
A thought just occured to me - is it possible that the bleed-down problem I am having is caused by the master cylinder/modulator somehow leaking inside? I am not familiar with their internals so maybe this is not possible.

Is it a possibility?
very possible, there's a bunch of orings inside...
 

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Discussion Starter #12
Considering the colour of the brake fluid and how clogged the master cylinder reservoir filter was nothing would surprise me at the moment.

I think that I will just leave well enough alone in the knowledge that it is all working well.

Thanks chaps
 

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If your pump only comes on every 20 min while the the key is in the run position. I'd say you have a pretty good seal. Mine comes on about ever 5 to 10 min and also kicks back in every 3rd brake application. To me, it sounds like everything is normal and your pump is fine.
 

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As mentioned, leave it alone cos it sounds good to go.
Though there are a few items that are seriously over looked, have a stroll through my blog and you'll see what I mean, take note of the Brake fluid res, lots of pics to make you scared of spending money
 

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Hi,

Me too have what you tell.

I was hoping that it was normal, like some describe, but no:

I try one 4.6 HSE, with a new pump fitted, I remember counting more then 5 "pedal press", before the pump kicks again.
The owner of the car tell me before the pump fails, he noted that the pumps runs about every every 4 a 5 minutes very shortly and then stop, if he leave the key in the 2 position (like mine), and also after a small stop, the pump kick in again.

So, perhaps your pump it´s not ok, but be "coollll", change the brake fluid (if you have not do that), and do/ask to do the brake bleed: http://www.rangerovers.net/maintenance/brakebleed4.html

I know I didn,t do that, so let´s see if the bleed make the diference.
 

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Discussion Starter #16
I did a complete brake fluid change back in February/March and that is when I noticed that something might not be right. I have installed a new accumulator. Of course a new pump will be tighter than ours and will get 5-6 pumps before the pump kicks in.

I will stay with 3 pumps or running every 20 minutes and be thankful.
 
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